Only a tiny minority of modern republics do not have a head of state; examples include the systems used in Switzerland and San Marino. While the Swiss system has a President of the Confederation, the headship of state is actually collectively vested in the seven-member Swiss Federal Council. The President is a member of the Federal Council elected by the Swiss Federal Assembly (the Swiss Parliament) for a year; and the President is merely primus inter pares (first among equals). Nevertheless, on the international stage he or she is treated as head of state. Letters of Credence appointing ambassadors are formally addressed to him or her by other heads of state.

In states with what is called a Presidential system of government, the President is also the head of government, as well as the head of state. Countries with such a system include the United States and most nations in South America. In this system the office of President is very powerful, both in practice and theory. In the United States, the President is indirectly elected by an Electoral College made up of electors chosen by voters in the presidential election. In normal circumstances, each elector is committed to voting for a specified candidate, so that the people, in voting for each elector, is in effect voting for the candidate. However in the 2000 presidential election, though Al Gore won the more popular votes, George W. Bush managed to win more electoral votes in the Electoral College and so win the presidency.

Other states have what is called a Parliamentary system of government, in which the President is only head of state, and the Prime Minister is the head of government. Countries with such systems include India, Ireland and Italy. Under such a system, executive authority if often vested in the president, with the Government governing in his or her name. However a president may also possess some reserve powers.

In parliamentary systems, the president's role is usually primarily ceremonial. However, due the combination of constitutionally established "reserve powers," protocol (which may require them to formally chair cabinet meetings and/or have access to all cabinet memoranda), and his or her role as the person in whose name executive authority is vested, often gives the president a degree of informal influence not often publicly realised.

A third system is the semi-presidential system, also known as the French system, in which like the Parliamentary system there is both a President and a Prime Minister, but unlike the Parliamentary system the President has significant day-to-day power. When his party controls the majority of seats in the National Assembly the president can operate closely with the parliament and prime minister, and work towards a common agenda. When the National Assembly is controlled by opponents of the President however, the president can find himself marginalized with the opposition party prime minister exercising most of the power. Though the prime minister remains an appointee of the president, the president must obey the rules of parliament, and select a leader from the house's majority holding party. Thus, sometimes the president and PM can be friends, sometimes bitter rivals. This situation is known as cohabitation. The French semi-presidential system, which can be considered a hybrid between the first two, was developed at the beginning of the Fifth Republic by Charles de Gaulle. It is used (of course) in France, Russia, and several other post-colonial countries which have emulated the French model.

Between 1870 and 1940, and again from 1945 to 1958, France operated a classic parliamentary system of government, with power in a cabinet chosen by the National Assembly, and a largely though not totally symbolic president. In 1877, President MacMahon showed that his office was constitutionally significant when he dismissed the then prime minister before calling new elections, in the hope of achieving a royalist majority to restore the monarchy. (In earlier periods, France operated under systems of absolute monarchy (pre the 1789 revolution), constitutional monarchy (1815-1848), a presidential system (1848-52) and an empire (early 1800s to 1815; 1852-1870).

In dictatorships, the title is frequently taken by self-appointed and/or military-backed leaders. Such is the case in many African states; Idi Amin in Uganda, for example. Sometimes the title is even extended into the more presumptuous form of "president for life." In some communist states the head of the Communist party was also given the presidency, Fidel Castro in Cuba, Mikhail Gorbachev in the Soviet Union. On other occasions in the Soviet Union, the real power was exercised by the General Secretary of the Communist Party, with some local notable holding the presidency.

As the country's head of state, in most countries the president is entitled to certain symbolic honors, as well as luxury perks that come with the office. For example, most of the world's presidents have a special residence; often a lavish mansion or palace. The President of the United States for example resides in the famous White House.

As well as an official residence, in some nations the Presidency brings with it certain symbols of office, such as an official uniform, decorations, or other accessories. Perhaps the most common presidential symbol are the presidential sashes worn by the presidents of South America. In these countries, the sash is a symbol of the presidency's continutiy, and presting the sash to the new president is a key part of the inauguration ceremony.

President is also used as a title in a number of non-governmental circumstances. The head of a university or non-profit corporation, particularly in the United States of America, is often known as president. President is also a title in many corporations. In some cases the president acts as chief operating officer[?] under the direction of the chief executive officer.